Objective: To describe the development of the University of North Carolina (UNC) TR x ANSITION Scale that measures the health-care transition and self-management skills by youth with chronic health conditions. Methods: Item and scale development of the UNC TR x ANSITION Scale was informed by two theoretical models, available literature, and expert opinion interviews and feedback from youth with chronic conditions, their parents, and interdisciplinary collaboration. Through an iterative process, three versions of the scale were piloted on a total of 185 adolescents and emerging adults with different chronic illnesses. This clinically administered scale relies on a semi-structured interview format of the patient and does not rely solely on patient report, but is verified with information from the medical record to validate responses. Results: Following the item development and the three iterations of the scale, version 3 was examined in a more intensive fashion. The current version of the UNC TR x ANSITION Scale comprises 33 items scattered across the following 10 domains: Type of illness, Rx¼medications, Adherence, Nutrition, Self-management, Informed-reproduction, Trade/ school, Insurance, Ongoing support, and New health providers. It requires approximately 7-8 min to administer. With a sample of 128 adolescents and young adults, ranging in age from 12 to 20, inter-rater reliability was strong (r ¼ 0.71) and item-total correlation scores were moderate to high. Content and construct validity were satisfactory, and the overall score was sensitive to advancing age. The univariate linear regression yielded a beta coefficient of 1.08 (p < 0.0001), indicating that the total score increased with advancing age. Specifically, there was about a one point increase in the total score for each year of age. Conclusion: The UNC TR x ANSITION Scale is a disease-neutral tool that can be used in the clinical setting. Initial findings suggest that it is a reliable and valid tool that has the potential to measure health-care transition skill mastery and knowledge in a multidimensional fashion.